In use the resilient packer of an annular blowout preventer can wear and be damaged. Changing the packer in present annular blowout preventers requires the removal of the upper end connection plus other elements of the BOP stack which are above the annular preventer such as the bell nipple, stripper, or rotating head. To do this clearance must be provided between the rig floor substructure and the top of he BOP to allow the top to be lifted clear to provide access to the packer. This is very inconvenient in snubbing operations. Also the top portion of most present annular blowout preventers is large and heavy which reduces the clearance and increases the difficulty of replacing the packer.
U.S. Pat. No. 2,154,955 discloses a well casing control valve having removable side plates allowing access for ram changes.
U.S. Pat. No. 2,320,974 discloses a ram type blowout preventer with removable side plates for changing internal ram operating mechanisms and rams.
U.S. Pat. No. 2,592,197 discloses a ram type blowout preventer with side windows for each ram for insertion and removal of the rams with covers secured over the windows for each ram for insertion and removal of the rams with covers secured over the windows.
None of the known prior art recognizes the problem of changing the annular packer in an annular blowout preventer. Flat door covering windows for access to rams in a ram type blowout preventer do not teach that the packer of an annular blowout preventer could be removed in a manner other than through the top.